U.S. patent number 4,413,829 [Application Number 06/350,022] was granted by the patent office on 1983-11-08 for shaft sealing assembly.
This patent grant is currently assigned to Howaldtswerke-Deutsche Werft Aktiengesellschaft Hamburg und Kiel. Invention is credited to Gunter Pietsch.
United States Patent |
4,413,829 |
Pietsch |
November 8, 1983 |
Shaft sealing assembly
Abstract
A shaft sealing assembly containing a liquid lubricant uses an
arrangement hich can accommodate shaft-eccentricities and vibratory
movements which cause radial deflections of the shaft, without
impairing the efficiency of sealing of the assembly. The assembly
is of a type using a housing in which two flexible sealing rings
are spaced apart from each other and mounted to be stationary on
the shaft, at least one sealing ring being supported by a mounting
ring. The mounting ring is capable of radially being displaced
within the housing, when there is shaft-eccentricity, or when
radial vibratory movements of the shaft occur. The mounting ring is
nonrotatably supported from the inside of the housing by a
resilient annular wall made of a sealing material. The arrangement
comprises at least one inner annular chamber containing the liquid
lubricant, and at least one outer annular chamber disposed radially
outside the mounting ring, the two annular chambers being provided
with a connecting fluid passage. Rotation of the shaft causes the
lubricant from the inner chamber to be guided by deflectors into
the outer chamber via the fluid passage. The lubricant is cooled in
the outer chamber and led back into the inner chamber. The shaft
sealing assembly is particularly useful as an aft-stern tube seal
of a vessel, providing seal-safety and long seal-life.
Inventors: |
Pietsch; Gunter (Hamburg,
DE) |
Assignee: |
Howaldtswerke-Deutsche Werft
Aktiengesellschaft Hamburg und Kiel (Hamburg,
DE)
|
Family
ID: |
6125350 |
Appl.
No.: |
06/350,022 |
Filed: |
February 18, 1982 |
Foreign Application Priority Data
|
|
|
|
|
Feb 20, 1981 [DE] |
|
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3106318 |
|
Current U.S.
Class: |
277/504; 277/563;
277/930 |
Current CPC
Class: |
B63H
23/321 (20130101); F16J 15/162 (20130101); F16J
15/324 (20130101); B63H 2023/327 (20130101); Y10S
277/93 (20130101); F16H 57/0472 (20130101) |
Current International
Class: |
B63H
23/00 (20060101); B63H 23/32 (20060101); F16J
15/32 (20060101); F16J 15/16 (20060101); F16C
033/74 (); F16J 015/40 () |
Field of
Search: |
;277/30,59,15,3,22 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Smith; Robert I.
Attorney, Agent or Firm: Lewis; Jon M.
Claims
What is claimed is:
1. A shaft sealing assembly for sealing a shaft extension emerging
from a housing which is at least partly cylindrical, the assembly
comprising: at least one lip type sealing element disposed within
said housing for making a seal on the shaft extension to be sealed,
said sealing element being fastened to and supported by a mounting
ring means of composite construction, said mounting ring means
being disposed substantially coaxially with the shaft, said
mounting ring means in turn being nonrotatably supported within
said housing by an annular shaped resilient wall member, said
annular shaped wall member being fastened along its outer periphery
to an inside surface of said housing, whereby, by the flexing
action of said wall member, said mounting ring in use is capable of
radial displacements so as to accommodate any shaft-eccentricity
and vibratory radial displacements of said shaft extension, wherein
said mounting includes a plurality of ring elements fastened
together and supporting two of said sealing elements which are
axially spaced from each other and disposed on said shaft
extension, the shaft assembly including: an additional lip type
sealing element adapted to be disposed on said shaft extension and
supported by an end portion of said housing, said assembly
including a first annular shaped reservoir chamber defined partly
by a surface of the shaft extension and partly by said at least one
sealing element and said additional sealing element and partly by
an inner surface of the mounting ring, said reservoir chamber
adapted to contain a liquid lubricant; an outer annular chamber
disposed radially outside of and substantially coaxial with said
first annular chamber, the assembly including a first liquid
passage in the form of a conduit interconnecting said first and
outer annular chambers, the shaft sealing assembly including a
first stationary deflector means supported by said mounting ring to
extend towards the shaft, said deflector means being so shaped as
to cause a whirl of said liquid lubricant and force the lubricant
from said first annular shaped reservoir chamber to said outer
annular chamber via said first liquid passage.
2. Shaft sealing assembly as in claim 1, including a second
stationary deflector means supported on an outer surface of the
mounting ring and disposed extending radially away from the shaft,
the assembly further including at least a second fluid passage in
the form of a conduit interconnecting said first reservoir chamber
and said outer chamber, the second fluid passage being so disposed
as to assist return of the liquid lubricant from the outer chamber
to the first reservoir chamber for recirculation of the liquid
lubricant.
3. Shaft sealing assembly as in claim 2, wherein said first and
second stationary deflector means are members having a Y shaped
cross-section being supported by the mounting ring in a manner not
totally impeding circumferential flow of liquid lubricant in the
first chamber and said outer chamber.
4. Shaft sealing assembly as in claim 2, wherein said mounting ring
comprises material selected from a group comprising polyamide,
polyethylene, polyvinylchloride and combinations thereof.
5. A shaft sealing assembly according to claim 1 including
additional second circulation system comprising second inner
annular chamber for a lubricating liquid; a second outer annular
chamber for cooling the lubricating liquid of the second inner
annular chamber; a resilient wall for separating said first and
second outer annular chambers, channels for connecting the second
inner and outer annular chambers, and deflector elements arranged
in second inner and outer annular chambers.
6. A shaft sealing assembly according to claim 1 wherein a bush is
fastened nonrotatably to the shaft in close fitting therewith,
wherein the housing includes radial internal faces, wherein said
mounting ring is borne on the bush and is radially movable within
the housing, the assembly including clearances between said radial
faces of the housing and said mounting ring, said clearances being
lubricated by circulating liquid thereby forming further passages
for said circulating liquid.
7. A shaft sealing assembly for sealing a shaft extension emerging
from a housing which is at least partly cylindrical, the assembly
comprising: at least first and second lip type sealing elements
which are axially displaced and disposed on the shaft extension, at
least one of said sealing elements being fastened to and supported
by a mounting ring means, said mounting ring means being disposed
substantially coaxially with the shaft and the cylindrical portion
of said housing, said mounting ring in turn being nonrotatably
supported within the cylindrical portion of said housing by a
substantially annular shaped, resilient wall member, said wall
member being chemically resistant to liquid lubricant, for
lubricating at least said assembly, said wall member per se being
fastened along its outer periphery to an inside surface of the
cylindrical portion of the housing; an inner annular chamber for
containing said liquid lubricant and being formed between the shaft
surface and an inner periphery of the mounting ring; an outer
annular chamber formed between an outer surface of the mounting
ring and an inner surface of the housing; first and second conduits
in the form of liquid passages through the mounting ring and
establishing fluid connection between said inner chamber and said
outer chamber; means responsive to the shaft rotation for causing a
whirl of the liquid lubricant in said inner annular chamber to
force the liquid lubricant through one of said conduits into said
outer chamber for facilitating cooling of the liquid lubricant, the
other of said conduits for returning the liquid lubricant to the
inner chamber for recirculation, whereby, by the flexing action of
the resilient wall member, the mounting ring in use is capable of
radial displacements to accommodate any shaft-eccentricity and
vibratory radial displacements of the shaft extension.
8. A shaft sealing assembly for rotating shafts comprising:
(a) a rotatable shaft and a bush fastened to the shaft,
(b) a non-rotating mounting ring surrounding the bush,
(c) a housing in which the mounting ring is radially movably
accommodated, said housing containing a liquid lubricant,
(d) two sealing rings spaced apart axially from one another and
sealing against the bush, one of said sealing rings being arranged
in the mounting ring,
(e) an inner annular chamber for containing said liquid lubricant,
the inner annular chamber being defined at least partly by said
sealing rings, the mounting ring and the bush,
(f) an outer annular chamber for cooling said liquid lubricant
which outer annular chamber is formed between the mounting ring and
the housing,
(g) channels in the form of conduits in the mounting ring for
connecting the inner and outer annular chambers, and
(h) means for circulating said liquid in and between both said
annular chambers by rotation of the shaft, said circulating means
comprising a stationary deflector element in the inner annular
chamber and another stationary deflector element in the outer
annular chamber, both the deflector elements narrowing the
cross-section of said circular chambers and forcing a part of said
liquid lubricant in one chamber to flow to the other chamber.
Description
BACKGROUND OF THE INVENTION
The invention relates to improvements in shaft sealing assemblies
in which at least two sealing rings within a housing are spaced
part from each other and seal against a rotating shaft or against a
bush fastened on a rotating shaft, wherein the sealing rings are
lubricated by a liquid lubricant in at least one annular chamber
between the sealing rings. The invention is applicable particularly
to aft-stern tube seals of vessels.
Shaft sealing assemblies of the foregoing type have widespread
applications in protecting a rotating shaft-end which emerges from
a housing which has to be protected against ingress of moisture,
dirt, dust and other contaminants. While innumerable shaft sealing
arrangements are known in the prior art ranging from the simplest
to those which are very sophisticated, the known sealing
arrangements cater to specific requirements and operating
conditions and are not universally suitable for all applications.
Specifically, while reckoning the functional requirements of shaft
seals for aft-stern tube seals of ships, cognizance must be taken
of the fact that the seal should function effectively and providing
a long life in a very hostile and unfavorable operating environment
which includes enormous turbulence of the water in which the ship
travels, as also the abrasive particles such as silt or sand and
other pollutants or chemicals which might have contaminated the
water. The shaft seal for aft-stern applicants should also
withstand deleterious vibrations and effects of shaft-eccentricity,
without creating a need for frequent and premature replacement of
the sealing lubricant within the shaft sealing assembly. Frequent
replacements of the shaft sealing lubricant with clean sealing
lubricant is cumbersome and uneconomical; besides, any need for
frequent lubricant replacement indicates that the shaft seal is
letting in ingress of contaminants because of deterioration. The
present invention is directed to providing an effective shaft
sealing assembly such as for an aft-stern seal of a vessel, to
withstand against vibrations and shaft-eccentricity in
particular.
DESCRIPTION OF PRIOR ART
In the prior U.S. Pat. No. 3,936,057, a shaft seal is described in
which a liquid lubricant, circulated in an annular space by the
rotation of the shaft, is forced by a deflector element to flow
through conduit-like passages to a tank for cooling the lubricant.
This lubrication and cooling system works reasonably well but is
mainly limited in application to only the forward seal of stern
tube bearings. The arrangement necessary for aft-stern tube seals
cannot be sufficiently protected against damage by
shaft-eccentricity or bending of the shaft or other external
influences, if the hitherto known shaft seal assembly is used.
SUMMARY OF THE INVENTION
Known prior art arrangements including the shaft seal assembly
taught in the U.S. Pat. No. 3,936,057 have had a potential
disadvantage in that the mounting ring which supports at least one
of first and second sealing members radially inwardly (of the
mounting ring) was substantially rigidly mounted within the
assembly housing. Consequently, over a period of use, the shaft
seal assembly after being subjected to forces of
shaft-eccentricity, vibratory forces and other external factors
would deteriorate, allowing ingress of contaminants, thus leading
to a total premature destruction of the shaft seal assembly. The
mounting ring in accordance with the broad concept of this
invention is made of a hard light material, for example, hard
plastics, and is mounted within the housing by using a resilient
annular wall which extends from the outside periphery of the
mounting ring to an inside periphery of the housing. Thus, the
mounting ring is capable of undergoing radial movements in all
directions, thereby accommodating shaft-eccentricity and vibratory
movements of the shaft.
The present invention in its broad form comprises a shaft sealing
assembly for sealing a shaft extension emerging from a housing
which is at least partly cylindrical, the assembly comprising: at
least one lip type sealing element disposed within said housing for
making a seal on the shaft extension to be sealed, said sealing
element being fastened to and supported by a mounting ring means,
said mounting ring means being disposed substantially coaxially
with the shaft, said mounting ring means in turn being nonrotatably
supported within said housing by an annular shaped resilient wall
member, said annular shaped wall member being fastened along its
outer periphery to an inside surface of said housing, whereby, by
the flexing action of said wall member, said mounting ring in use
is capable of radial displacements so as to accommodate any
shaft-eccentricity and vibratory radial displacements of said shaft
extension.
In a preferred embodiment described herein, there is provided a
shaft sealing assembly in which at least one inner annular chamber
is formed between two axially spaced sealing rings; also provided
are a bush rotating with the shaft and a mounting ring surrounding
the inner annular chamber, in which the liquid lubricating the
sealing rings is deflected by the rotation of the shaft and is
forced to circulate through passages to and back from a cooling
zone; the cooling zone advantageously comprises an outer annular
chamber surrounding the mounting ring and is inside the housing of
the assembly, the housing per se, in use, being cooled by a
surrounding medium such as sea water. Expediently, the circulation
of the lubricating liquid is forced by separate deflector elements
which are positioned in the inner chamber as well as in the outer
annular chamber. Other alternative means narrowing the
cross-section of the inner annular chamber can be used to deflect
the lubricating liquid.
A mounting ring, in which at least one of the sealing rings is
positioned, is borne on the bush and is radially movable within the
housing so that it can follow all radial movements of the shaft,
for example, induced by vibrations. The axial clearances or gaps
between the radial faces of the mounting ring and the corresponding
faces of the housing can be so that small deviations of the axis of
the housing from the axis of the shaft or tilting movements are
possible. These gaps form further radial passages for the
lubricating liquid and are lubricated by the liquid. The mounting
ring is preferably made of a hard plastic material such as
polyamide, polyethylene, polyvinylcholoride and combinations of
such plastics. Such a light-weight mounting ring follows all
movements of the shaft very easily and ensures that the local
pressure of a lip sealing ring positioned in the mounting ring is
uniformly distributed over the circumferential contacting line
thereby reducing the danger of local overheating in the sealing
ring.
Between the mounting ring and the housing, at least one solid
resilient annular wall is provided. The resilient wall centers the
mounting ring inside the housing and expediently defines the outer
annular chamber at least on one side. The resilient wall preferably
extends substantially in a radial direction and prevents the
mounting ring from rotating with the shaft but permits radial and
tilting movements of the mounting ring inside the housing. In a
second embodiment, instead of a solid resilient annular wall, a
compressible inflatable tubular wall is used.
According to one illustrated embodiment of the invention, the shaft
sealing assembly comprises two inner annular chambers limited
partly by sealing rings, and two outer annular chambers separated
by a resilient wall, the first inner and outer chambers being
connected by channels to form a first lubricating and cooling
system; the second inner and outer chambers are provided with
intermediate channels and form a second lubricating and cooling
system. The lubricating liquids in both the systems can be
different, if desired.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional diagrammatic view of one half of
a shaft sealing assembly having a first and a second lubricating
and cooling system the inner and outer chambers of which are
connected by channels in a mounting ring, the mounting ring bearing
on a bush fastened to a shaft.
FIG. 2 is a radial sectional diagrammatic view along section II--II
in FIG. 1 and shows an inner and an outer annular chamber, the
passage channels between the chambers, and deflector elements.
FIG. 3 is a longitudinal diagrammatic sectional view of a second
embodiment showing one half of a shaft sealing assembly having a
first and a second lubricating and cooling systems, the outer
chambers of which are separated by a compressible tubular wall, the
assembly having means narrowing the cross-section of the inner
chambers to force-circulate the lubricating liquids through the
cooling systems.
FIG. 4 is a diagrammatic radial sectional view along section IV--IV
in FIG. 3 showing the means for circulating the lubricating liquid
and the passage-channels between inner and outer chambers.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the drawings there is shown in FIG. 1 an aft-stern
tube sealing assembly of a vessel in which a bush 2 is arranged on
a rotatable shaft 1 and is provided at one end with a flange 3 for
fastening to a propeller flange (not shown), the other end of the
shaft extending into a stern tube bearing (not shown). The sealing
assembly is mounted by means of a fastening flange 4 onto a stern
boss which is not shown. A cap 5 is fastened by any suitable means
such as screws (not shown) to a collar extending from the fastening
flange 4.
The fastening flange 4 and the cap 5 form the housing of the
sealing assembly. In the housing there is a mounting ring 6 which
surrounds the bush 2. As shown, the mounting ring 6 consists of
three ring parts 6a, 6b and 6c which are kept together by screws
(not shown). Preferably the parts of the mounting ring 6 are made
of a light material such as plastics. The mounting ring 6 is
radially movable within the housing; small axial and tilting
motions of the mounting ring are accommodated because of axial gaps
or clearances 9, 10 between the radial faces of the mounting ring 6
and of the fastening flange 4 respectively of the cap 5. The ring
part 6a is borne on the bush 2.
A sealing ring 7a is arranged on the mounting ring and is in
sealing contact with the bush 2. Axially spaced from the sealing
ring 7a there is another sealing ring 7c which is fastened to the
cap 5 by means of a lid 8 at the aft end of the assembly. The
sealing rings are preferably lip seals made of a resilient material
such as rubber. As shown, an inner annular chamber 11 for a liquid
lubricating the sealing rings 7a, 7c is defined by the bush 2, the
ring part 6b of the mounting ring 6 and by the sealing rings 7a and
7c.
An outer annular chamber 15 for cooling the liquid lubricating the
sealing rings 7a, 7c is shown formed between the ring part 6b of
the mounting ring 6 and the cap 5 which is a part of the housing.
The outer annular chamber 15 and the inner annular chamber 11 are
connected by two passages or channels 14 in the ring part 6b. In
the inner annular chamber 11 a deflector element 12 is positioned
between the channels 14. The deflector element 12 comprises two
resilient arms 13 the ends of which rest on the bush (FIG. 2). The
arms 13 of the deflector element 12 do not close the cross-section
of the inner annular chamber 11 and do not contact the sealing
rings 7a, 7c so that lubrication is not interrupted at the
deflector element, but, the lubricant rotating with the bush near
the lips of the sealing rings is deflected and whirled. The
deflector element forces some of the lubricating liquid rotating in
the inner annular chamber to flow through a channel 14 to the outer
annular chamber 15 as in shown in FIG. 2, and there the liquid is
cooled in the outer chamber of the housing outside which, in use,
there is a cooling medium such as sea water. In the outer annular
chamber 15 there is another deflector element 16 which leads the
liquid through the outer chamber and back to the inner annular
chamber 11. Some of the liquid flows also in substantially a radial
direction in the clearance 9 between the aft end of the mounting
ring 6 and the radial inner area of the cap 5. The deflector
element 16 is similar to the deflector element 12 described before,
and both are mounted in grooves of ring part 6b of mounting ring
6.
The embodiment according to FIG. 1 comprises a second lubrication
and cooling system with a second inner annular chamber 17, a second
outer annular chamber 19, further channels 14, and deflector
elements 18 and 20. The second inner annular chamber 17 extends
axially between a sealing ring 7b mounted to the mounting ring 6
and the aft end of the stern tube bearing which is not shown. The
second lubrication and cooling system can communicate with the
lubrication of the stern tube bearing so that the oil of that
bearing lubricates also the sealing ring 7b and is present also in
the second inner and outer annular chambers 17, 19 respectively.
However, a further sealing ring 7d as shown in FIG. 3 for
separating the second system from the stern tube bearing can be
provided. The first and second outer annular chambers 15, 19 are
separated by a resilient wall 21 which also prevents the mounting
ring 6 from rotation. Different lubricating liquids can be used in
the first cooling system comprising the annular chambers 11, 15 and
the second cooling system comprising the second annular chambers
17, 19. In any case the resilient wall 21 prevents sea water which
occasionally may enter the first system from coming into the second
lubrication system.
If lubrication of the ring part 6a of the mounting ring 6 is
necessary, some lubricant can flow through a channel 22 connected
by a flexible pipe 23 from a supply source which is not shown.
In the embodiment according to FIGS. 3 and 4, in which the same
reference numerals are used, the flow of the lubricating liquids
from the inner annular chambers 11, 17 to the outer annular
chambers 15, 19 respectively is achieved by elements 24, 25
inserted in the inner chambers and narrowing their cross-section.
At the narrowest sections of the inner chambers outlet channels 26
lead the lubricating liquid to the outer chambers 15, 19; at a
diametrically opposite point, inlet channels 27 are positioned
through which the cooled liquid lubricant returns to the inner
chambers 11, 17.
In this example the outer annular chambers 15, 19 are separated by
a tubular wall 28 of resilient material. The tubular wall 28 is
compressible by radial movements of the mounting ring and by
expansion of the liquids included in the first and in the second
lubrication systems. Furthermore, it is possible to inflate the
resilient tubular wall by compressed air or by a liquid through a
pipe (not shown) from a supply source inside the ship.
A conduit passage 29 can be provided in the housing 4, 5 which
leads from the first outer annular chamber to a control valve or a
safety valve inside the ship (not shown) so that the quality of the
lubricating liquid in the first lubrication system can be checked.
Another pipe 30 in the fastening flange 4 can be provided for
inspecting the second lubrication system. For each lubrication
system two pipes, 29 resp. 30 can be used so that it is possible to
replace the lubricating liquid after a predetermined length of
time, or sooner if necessary.
The pressure head caused by pressure differences of the lubricating
liquid in a lubrication and cooling system caused by deflector
elements or other means for circulating is relatively small, and
therefore it is preferable that the passages or channels 14, 26, 27
are very short (so as to require a low pressure head for fluid
flow). Furthermore, these channels in the mounting ring 6 cannot
usually break or become squeezed off. The volume of the outer
annular chambers 15, 19 can be much greater than that of the inner
annular chambers 11, 17 so that sufficient cooling of the liquid is
achieved and a substantial amount of liquid can be present in a
closed system without need of replacing it frequently. The wear of
the essential sealing rings 7a, as also the ingress of water into
the stern tube bearing and 7b against exudation of oil from the
bearing are both reduced because rings 7a and 7b are mounted in the
mounting ring 6 which can radially move and follow all eccentric
motions of the shaft, and also because the rings 7a, 7b are
lubricated by a cooled lubricant. Thus the life of the sealing
rings is substantially lengthened.
The invention is not restricted to stern tube seals, as other
shafts of watercraft, water power machines, etc. can be sealed in
the described manner, and within the scope of the invention are
also further embodiments having more than two outer and inner
annular chambers, other type of sealing rings or further
variations.
The invention is not to be taken as limited to all the details
thereof described hereinabove, since modifications and variations
thereof may be made without departing from the scope of the
invention.
* * * * *